1. Field of the Invention
The present invention relates to an inkjet printhead substrate used in an inkjet print head that performs recording by discharging ink droplets from discharge ports and to a method for manufacturing the inkjet printhead substrate. The present invention also relates to an inkjet print head including such an inkjet printhead substrate and to an inkjet recording apparatus including such an inkjet print head.
2. Description of the Related Art
An example of the inkjet print head has an inkjet recording chip as shown in FIGS. 8A to 8C.
FIGS. 8A to 8C are a plan view, a bottom view, and a side view of an inkjet recording chip 61, respectively. The inkjet recording chip 61 has a through hole (ink supply port) 62 for supplying ink from the back surface thereof.
A plurality of rows of heat generating elements (not shown) that apply discharging energy to ink are arranged on both sides of the through hole 62 in the surface of the inkjet printhead substrate 11.
In addition, a discharge-port plate 12 is provided on the inkjet printhead substrate 11. The discharge-port plate 12 has a plurality of discharge ports 13 facing the heat generating elements.
A plurality of electrode pads 14 electrically connected to the heat generating elements are arranged at both ends of the surface of the inkjet printhead substrate 11.
Referring to FIG. 9, the electrode pads 14 provided on the inkjet printhead substrate 11 and a plurality of electrode leads 72 provided on a flexible film wiring substrate 71 are electrically connected by, for example, tape automated bonding (TAB). Thus, an inkjet recording element unit 73 is formed.
The inkjet recording element unit 73 includes contact pads 74 used for connection to a recording apparatus. In FIG. 9, regions enclosed by dashed lines and denoted by reference numeral 15 are to be coated and protected by a sealing resin after the electrode pads 14 and the electrode leads 72 are connected.
Then, as shown in FIG. 10, the recording element unit 73 is attached to an ink tank 81. To protect the electrically connected portions of the electrode pads 14 and the electrode leads 72 in the recording element unit 73 from corrosion due to ink or wire breaking due to externally applied force, the entirety of the connected portions are coated and protected by a sealing resin 82. Thus, an inkjet print head 83 is completed. The contact pads 74 are used to connect the inkjet print head 83 to the inkjet recording apparatus.
In such an inkjet print head, a problem due to ink leakage from the discharge ports sometimes occurs. Japanese Patent Laid-Open No. 7-60954 discloses a technique in which an ink-leakage detection sensor is provided on a flexible substrate.
However, the recording head is heated when driven and cooled when not driven. The heat causes the components constituting the inkjet print head to alternately undergo slight expansion and contraction.
In the electrically connected portions, because the linear expansion coefficients of the inkjet printhead substrate and the sealing resin are different, separation occasionally occurs at the interface between the inkjet printhead substrate and the sealing resin.
Furthermore, when such an inkjet print head is used for a long time in, for example, a high-temperature and high-humidity environment, the sealing resin is gradually degraded, sometimes resulting in separation occurring at the interface between the inkjet printhead substrate and the sealing resin.
As a result, ink sometimes penetrates into the electrically connected portions of the electrode pads provided on the inkjet printhead substrate and the electrode leads provided on the flexible film wiring substrate, resulting in malfunction such as print failure. Thus, there is a problem in that ink and sheets are wasted during continuous printing.